Automagically execute a bash function/cmd upon entering a directory.

After growing tired of sourcing Petalinux/Yocto-project settings, I decided to compile a script/code that resides under my ~/.bashrc , the only thing the code/script does it automagically source my settings upon entering the directory else it will just list the contents of that directory.

source $HOME/.opt/Xilinx/Vivado/2017.2/settings64.sh
export YOCTODIR=$HOME/Documents/Xilinx/EmbeddedLinux/Yocto/poky
export PETADIR=$HOME/Documents/Xilinx/EmbeddedLinux/Petalinux
function cd {
    # The 'builtin' keyword allows you to redefine a Bash builtin without
    # creating a recursion. Quoting the parameter makes it work in case there are spaces in
    # directory names.
    builtin cd "$@"
    if [ "$PWD" == "$YOCTODIR" ] ;
        then
            bash $YOCTODIR/.source_yocto
    elif [ "$PWD" == "$PETADIR" ] ;
        then
            bash $PETADIR/.source_petalinux
    else
        ls -lhF;
    fi
}

The content of source_petalinux listed above.

$ cat $PETADIR/.source_petalinux
#!/bin/bash
. ~/.opt/petalinux/settings.sh

as well as .source_yocto

$ cat $YOCTODIR/.source_yocto

#!/bin/bash
. $HOME/Documents/Xilinx/EmbeddedLinux/Yocto/poky/oe-init-build-env
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My first experience with the ZedBoard SoC board.

I recently registered my Masters and part of my research includes the use of an FPGA for real-time network communications between smart grids. So I am faced with 2 things – learning a new environment as well as a different field (Power Systems) coming from an Electronics and Computer engineering background.

I am the type of person that is always eager to learn new things, so being thrown into the deep end is nothing foreign to me, sounds like something I took from my resume.

I was given this board – and I needed to familiarise myself with it.

This blog will detail my experiences and hacks.

zedboard-2zedboard box

Getting started with the ZedBoard SoC

Firstly, we will need to download Xilinx Vivado suite, in order to do this we go to the Xilinx Downloads page to obtain the installer.
Select version 2017.2 or later on the left sidebar. I used the “Single File Download” option and chose “Vivado HLx 2017.2: All OS installer Single-File Download”. It is a tarball that is 22Gigs, yes there was no typo – 22Gigs large.
Note: You have to be a registered user to download it.

Once the download is completed, untar the tarball, cd into the extracted directory, and execute the GUI installer.

# Confirm the file is valid by checking the md5 hash
# MD5 SUM Value: 958f190a089ad3f39d327d972c7dcf35
$ md5sum Xilinx_Vivado_SDK_2017.2_0616_1.tar.gz
# Once that is confirmed untar and install
$ tar -zxvf Xilinx_Vivado_SDK_2017.2_0616_1.tar.gz
$ cd Xilinx_Vivado_SDK_2017.2_0616_1
$ sudo dpkg --add-architecture i386
$ sudo ./xsetup

Agree to the terms of use and select “Vivado HL WebPACK Edition”. Next, tick also Xilinx Software Development Kit (SDK) on the next page, since it’s free and very useful.

Note: by default, Vivado is installed into the /opt/Xilinx/Vivado/2017.2 directory.

At the end of the installation, the license manager will ask for a license. The “Obtain a license” button in the license manager if that does not work, just go to Xilinx Licensing site directly and get a WebPACK license and install it.

Once done with the installation, we need to install the JTAG cable drivers that are needed for many purposes e.g. programming the hardware.

cd /opt/Xilinx/Vivado/2017.2/data/xicom/cable_drivers/lin64/install_script/install_drivers
sudo ./install_drivers

Now, change the ownership of the ~/.Xilinx directory so that you may use Vivado without superuser privilege:
sudo chown -hR $USER:$USER $HOME/.Xilinx/

Every time you want to fire up Vivado, remember to source the “settings” scripts to have the right environment variables:

source /opt/Xilinx/Vivado/2017.2/settings64.sh
source /opt/Xilinx/SDK/2017.2/settings64.sh

Lazy people like myself prefer to uncomplicate the complicated, to avoid executing the above commands each and everytime one needs to start Vivado – do the following.

echo "source /opt/Xilinx/Vivado/2017.2/settings64.sh" >> ~/.bashrc
echo "source /opt/Xilinx/SDK/2017.2/settings64.sh" >> ~/.bashrc
source ~/.bashrc

When done, start-up Vivado from the command line:
vivado or SDK: xsdk

Quoting Raymond Hettinger, While hitting the podium and “There must be a better way!”

Create a new file called vivado.desktop

sudo vim /usr/share/applications/vivado.desktop
# Copy the contents to the file

[Desktop Entry]
Type=Application
Version=1.0
GenericName=Vivado
Name=Vivado
Comment=Vivado
TryExec=/opt/Xilinx/Vivado/2017.2/bin/vivado
Exec=/opt/Xilinx/Vivado/2017.2/bin/vivado
Icon=
Terminal=false
Categories=Education;System
StartupNotify=false
X-GNOME-Autostart-Delay=5

When done, log out-in in order to refresh the systems settings.

Vivado should be available from start-menu and can be copied to the desktop for future executions.

Allow users of a certain group to run a command without sudo passwd

Time to time I usually find myself typing sudo to execute commands requiring sudo rights, and this is repetitive which simply means one gets weary of typing sudo password every time, hence this blog post. Reason for this is to remind me how to do it the next time I am faced with such conundrum(s).

Suppose I wanted to add a group of users who are allowed to run mount and umount without passwords. So I first want to add a group called “staff”

sudo groupadd staff

Next we need to edit the /etc/group and add the users

staff:407:

will be present ,hence append users you want to add the users separated by commas.

staff:x:407:user1,user2,...

Now we need to configure sudo to allow members of the “staff” group to actually invoke the mount and umount commands.

You just need to add the following lines to /etc/sudoers or execute sudo visudo

%staff ALL=NOPASSWD: /sbin/mount, /sbin/umount

Now sudo mount won’t ask password but since it is a pain in the butt typing sudo all the time, we can avoid it by doing the following:

I can create the following script called “/usr/bin/mount” (and similar script for umount)

#! /bin/sh
sudo /sbin/mount $*

To make this slightly more secure, We might want to change the ownership of these scripts to the “staff” group.

chgrp staff /usr/bin/mount /usr/bin/umount

and then make them executable only for the group “staff”

chmod g+x /usr/bin/mount  /usr/bin/umount

Note:Depending on the OS you are using please check where mount and umount commands are located. It might be in /bin/ instead of /sbin.
So you might have to make necessary changes

 

Done

Setting up an MQTT server on Debian Jessie

Jolabs Tech Blog

Intro

Today we`re going to be setting up our own home automation server in a dedicated linux server. It’s gonna host our platform using the the Node.Js environment. The different devices around the house are going to be speaking MQTT to this server. I’ve chosen MQTT because of it’s robustness and lightweightness allowing for easy deployment on my favourite controllers: ESP8266. The esp-01, still the cheapest to this date,only sports 4mb of flash, has no trouble at all controlling a couple of relay’s for now. In the future the newer/bigger boards can be used to get more IO and function, but for now I’m going to be using the esp-01’s extensively around the house flexibly (it’s wireless…).

Requirements

The idea is to have the server online 24/7, so consider a computer thats not to power-hungry; like a Raspberry Pi or a small embedded box computer. Alternatively you can boot up…

View original post 340 more words

Move files by date into different directory using CLI

A while back I was unfortunate in such a way that my HDD that I primarily use as photo archive started having mechanical issues, and before It died on my arms I had the opportunity to backup most of my pictures, however most of them were truncated and had to be discarded and the ones I could recover their filenames where overwritten with random filenames and ascii codes.

For over a while I have neglected my pictures and they just piled up in a single and nameless directory, until I took it against myself to clean them up.

And one of the benefits of using Linux OS is the scripting features.

for i in *; 
do d=$(exiftool $i | grep 'Date/Time Original' | cut -f 17 -d ' '); 
newd=`echo ${d//:/-}`; 
echo $i ${newd} ;
mkdir -p ${newd}; 
mv -- ${i} ${newd}; 
done
  1. write this script to a file named mvByDate.sh in your old directory.
  2. replace the /your/new/directory with your new directory’s path
  3. make this file executable with chmod +x mvByDate.sh
  4. then execute this file by ./mvByDate.sh
  5. voila

Replacing A Failed Hard Drive In A Software RAID1 Array

Credit goes to Author:falko

Replacing A Failed Hard Drive In A Software RAID1 Array. This guide shows how to remove a failed hard drive from a Linux RAID1 array (software RAID), and how to add a new hard disk to the RAID1 array without losing data.

NOTE: There is a new version of this tutorial available that uses gdisk instead of sfdisk to support GPT partitions.

1 Preliminary Note

In this example I have two hard drives, /dev/sda and /dev/sdb, with the partitions /dev/sda1 and /dev/sda2 as well as /dev/sdb1 and/dev/sdb2.

/dev/sda1 and /dev/sdb1 make up the RAID1 array /dev/md0.

/dev/sda2 and /dev/sdb2 make up the RAID1 array /dev/md1.

/dev/sda1 + /dev/sdb1 = /dev/md0

/dev/sda2 + /dev/sdb2 = /dev/md1

/dev/sdb has failed, and we want to replace it.

2 How Do I Tell If A Hard Disk Has Failed?

If a disk has failed, you will probably find a lot of error messages in the log files, e.g. /var/log/messages or /var/log/syslog.

You can also run

cat /proc/mdstat

and instead of the string [UU] you will see [U_] if you have a degraded RAID1 array.

3 Removing The Failed Disk

To remove /dev/sdb, we will mark /dev/sdb1 and /dev/sdb2 as failed and remove them from their respective RAID arrays (/dev/md0 and/dev/md1).

First we mark /dev/sdb1 as failed:

mdadm --manage /dev/md0 --fail /dev/sdb1

The output of

cat /proc/mdstat

should look like this:

server1:~# cat /proc/mdstat

Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0] sdb1[2](F)
24418688 blocks [2/1] [U_]
md1 : active raid1 sda2[0] sdb2[1]
24418688 blocks [2/2] [UU]

unused devices:

Then we remove /dev/sdb1 from /dev/md0:

mdadm --manage /dev/md0 --remove /dev/sdb1

The output should be like this:

server1:~# mdadm --manage /dev/md0 --remove /dev/sdb1
mdadm: hot removed /dev/sdb1

And

cat /proc/mdstat
should show this:

server1:~# cat /proc/mdstat

Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0]
24418688 blocks [2/1] [U_]
md1 : active raid1 sda2[0] sdb2[1]
24418688 blocks [2/2] [UU]

unused devices:

Now we do the same steps again for /dev/sdb2 (which is part of /dev/md1):

mdadm --manage /dev/md1 --fail /dev/sdb2

then,

cat /proc/mdstat

server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0]
24418688 blocks [2/1] [U_]

md1 : active raid1 sda2[0] sdb2[2](F)
24418688 blocks [2/1] [U_]

unused devices:

mdadm –manage /dev/md1 –remove /dev/sdb2

server1:~# mdadm --manage /dev/md1 --remove /dev/sdb2
mdadm: hot removed /dev/sdb2

Now,
cat /proc/mdstat

server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0]
24418688 blocks [2/1] [U_]
md1 : active raid1 sda2[0]
24418688 blocks [2/1] [U_]

unused devices:

Then power down the system:

shutdown -h now

and replace the old /dev/sdb hard drive with a new one (it must have at least the same size as the old one – if it’s only a few MB smaller than the old one then rebuilding the arrays will fail).

4 Adding The New Hard Disk

After you have changed the hard disk /dev/sdb, boot the system.

The first thing we must do now is to create the exact same partitioning as on /dev/sda. We can do this with one simple command:

fdisk -d /dev/sda | sfdisk /dev/sdb

You can run

fdisk -l

to check if both hard drives have the same partitioning now.

Next we add /dev/sdb1 to /dev/md0 and /dev/sdb2 to /dev/md1:

mdadm –manage /dev/md0 –add /dev/sdb1

server1:~# mdadm --manage /dev/md0 --add /dev/sdb1
mdadm: re-added /dev/sdb1

mdadm –manage /dev/md1 –add /dev/sdb2

server1:~# mdadm --manage /dev/md1 --add /dev/sdb2
mdadm: re-added /dev/sdb2

Now both arays (/dev/md0 and /dev/md1) will be synchronized. Run

cat /proc/mdstat

to see when it’s finished.

During the synchronization the output will look like this:

server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0] sdb1[1]
24418688 blocks [2/1] [U_]
[=>...................]  recovery =  9.9% (2423168/24418688) finish=2.8min speed=127535K/sec

md1 : active raid1 sda2[0] sdb2[1]
24418688 blocks [2/1] [U_]
[=>...................]  recovery =  6.4% (1572096/24418688) finish=1.9min speed=196512K/sec

unused devices:

When the synchronization is finished, the output will look like this:

server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0] sdb1[1]
24418688 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
24418688 blocks [2/2] [UU]

unused devices:

That’s it, you have successfully replaced /dev/sdb!

Cool Bash Tricks

Create ~/.inputrc and fill it with this:

“\e[A”: history-search-backward
“\e[B”: history-search-forward

This allows you to search through your history using the up and down arrows … i.e. type “cd” and press the up arrow and you’ll search through everything in your history that starts with “cd”.

It’s a little bit like ctrl-r (mentioned in many of the comments below), but anchored to the start of the line, and the arrow keys allow you to scroll back and forth between matches.

I use it when I’m looking to (for instance) call up the last ping I did (hit p, up arrow, return), whereas I use ctrl-r more like search, when I’m trying to find a command based on an argument or option that I used.

Both useful.

Other options that I find useful to add:

set show-all-if-ambiguous on

This alters the default behavior of the completion functions. If set to ‘on’, words which have more than one possible completion cause the matches to be listed immediately instead of ringing the bell. The default value is ‘off’.

set completion-ignore-case on

If set to ‘on’, Readline performs filename matching and completion in a case-insensitive fashion. The default value is ‘off’.

(as miah points out below, this is all actually Readline functionality. The title should be “Readline is the single most useful thing in everything” 😉